The Carbon Footprint of
Personal Travel
News item. Tuesday 14th January. The government has decided to use public money to support Flybe. More disturbing than casual use of public funds to support failing business is the announcement of intention to review air passenger duty. As we argue below failure to tax aviation fuel is a distortion of the market in favour of the highest emissions forms of transport - another subsidy from an environmentally challenged future to a self-indulgent present. Air passenger duty represented a small step towards redressing the balance and encouraging transport modes with lower emissions. Flybe is a major operator of UK domestic routes where there are more rail and road alternatives.
News item. Tuesday 14th January. The government has decided to use public money to support Flybe. More disturbing than casual use of public funds to support failing business is the announcement of intention to review air passenger duty. As we argue below failure to tax aviation fuel is a distortion of the market in favour of the highest emissions forms of transport - another subsidy from an environmentally challenged future to a self-indulgent present. Air passenger duty represented a small step towards redressing the balance and encouraging transport modes with lower emissions. Flybe is a major operator of UK domestic routes where there are more rail and road alternatives.
Most readers of this blog are increasingly
environmentally conscious, particularly in relation to climate change.
Transport may not be the largest source of greenhouse gas emissions, but it is still a major contributor and in some respects one of the most difficult sectors to convert to low carbon alternatives. It also, in many instances, offers a lot of personal choice. So it is a worthwhile exercise to compare the environmental costs of the choices we, individually, make. The calculation can be complicated, but some very interesting ideas arise in the process of making the comparisons. My example will be the choice that a traveller to the South of France might face, assuming a 1250 mile or 2000 km return journey. These may represent very different experiences but for many people this is a real choice. The BBC recently published comparative tables, as shown below.
Transport may not be the largest source of greenhouse gas emissions, but it is still a major contributor and in some respects one of the most difficult sectors to convert to low carbon alternatives. It also, in many instances, offers a lot of personal choice. So it is a worthwhile exercise to compare the environmental costs of the choices we, individually, make. The calculation can be complicated, but some very interesting ideas arise in the process of making the comparisons. My example will be the choice that a traveller to the South of France might face, assuming a 1250 mile or 2000 km return journey. These may represent very different experiences but for many people this is a real choice. The BBC recently published comparative tables, as shown below.
These numbers are realistic,
at least as broad averages, and align quite closely to statistics quoted by other
sources. But there are a number of qualifications and observations that can be
made.
·
Numbers are invariably quoted for “average” or
typical flights, average aircraft or cars, and car journeys including urban
driving, and are not necessarily accurate for any particular journey, aircraft,
or road vehicle. This analysis also ignores the carbon footprint associated
with the manufacture of the cars, trains, buses or planes.
·
For the purposes of a simple comparison, we
should disregard the “marginality” argument, that if there are spare seats on
any form of public transport, then an individual decision to use that mode of
transport has near zero energy and environmental impact. This is technically
correct but the argument tells us little about the reality of transport
investment choices or what makes sense in policy terms.
·
Airline flights carry an additional penalty in
non-CO2 emissions, according to the BEIS
data. However the weighting of different GHG in terms of impact is itself a
complex issue. But this clearly a major factor.
·
The occupancy rate is crucial for all modes of
transport. The implicit and broadly justified assumption for air travel is that
typical flights are usually full. Trains
and buses tend to be more lightly loaded. The carbon footprint per passenger
mile for the car depends on the number of passengers in addition to the driver.
Two in the car halves the footprint as a first approximation.
·
For the car the assumed average is the overall
driving average in all conditions including urban and secondary roads. For a typical
long journey, on trunk roads and French autoroutes with minimal congestion, and
observing or staying a little below the speed limits, one should expect a
typical modern diesel car to produce emissions much closer to 130g per km, as
compared to the quoted 171g.
·
The other critical assumption is the fuel
source for electricity generation (in the case of the train). However the
calculation should relate to the incremental power generation induced by the
mode of transport, not necessarily the average fuel input per kWh. This would
considerably reduce the apparent advantage of the French railways, if
incremental load is generated from fossil fuels.
·
The table does not include electric vehicles.
If it did the same question would apply – of dependence on how the
electricity is generated. On the basis of current UK sources of generation this suggests a CO2 footprint of about 80g per km for small EVs, as
compared to 171g per km for average petrol/diesel vehicles (driver only in each case).[1]
If electricity production can be made carbon-free then the ideal is any mode of transport that is electricity based. This simply reflects the now widely accepted view that the path to decarbonising transport rests on the decarbonisation of electricity followed by the penetration of electricity into the transport market.
If electricity production can be made carbon-free then the ideal is any mode of transport that is electricity based. This simply reflects the now widely accepted view that the path to decarbonising transport rests on the decarbonisation of electricity followed by the penetration of electricity into the transport market.
And the environment friendly choice
between flight and a conventional car journey?
If the individual has a petrol
or diesel car, and the choice is between car and air travel, then, purely in
terms of CO2, the choice is finely balanced for a single occupancy
car as against a flight. However the inclusion of non-CO2 impacts
shifts the balance decisively in favour of the car. Additional passengers have
an even greater effect, with two people
in the car halving its emissions[2]. The flight is associated
with emissions equivalent to 254g per passenger mile, and the car journey with
only 65g per passenger mile. For a family of four on my hypothetical return
journey of 2000 km, the carbon footprint is approximately 2.0 tonnes for the
flight, but only 0.5 tonnes for the car journey.
So purely on an
environmental perspective, the preference should be clear.
Current policies discriminate
in favour of air travel and against the car
Of course there are several
factors that can determine choice of travel mode, including convenience – which
strongly favours flying, but in a world that clearly requires progress towards
low or zero emissions, one might expect that the costs and prices of the alternatives would at least reflect the huge additional environmental cost of flying. But
this is not the case.
Car drivers pay very substantial
fuel taxes, while aviation fuel is tax-free, and it takes little effort to work
out that in many instances flying will be cheaper than driving. Advance booking
for a flight from London to Nice, for example, can cost as little as £100
return fare. This is a perverse incentive, and continues to be responsible for
a very substantial environmental cost, which I have previously argued could be
valued at a sequestration cost [3] of at least £75, will fall heavily on an increasingly
near future.
The cost of cheap air travel
Cheap air travel has brought great
and welcome opportunities for mass market leisure travel, but its cost has been
so low that it has also hugely expanded the volume of travel and significantly changed
lifestyles. Wealthy British families can routinely travel to their second homes
in France for a weekend. Others routinely commute weekly by air between work in
one European city and home in another. And young men from London organise stag
weekends in Las Vegas.
Failure to reach international
agreement on the taxation of aviation fuel has in consequence resulted in a
subsidy from an environmentally challenging future to what some might see as a
self-indulgent present.
Time to find a sustainable solution? Electric aircraft are starting to look like a credible option, at least for short-haul. Otherwise it will have to be synthetic fuels (from an electric route) with a limited amount of sustainable biomass.
[1]
The difference is largely attributable to the substantial proportion of low
carbon generation in the UK.
[2] In
fact extra passengers have a small effect on fuel consumption, so this is a
small but not very significant exaggeration.
[3] I have previously suggested a figure of $200 per tonne to represent a minimal realistic cost of future carbon extraction from the atmosphere.